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The MMPI (Minnesota Multiphasic Personality Inventory), composed by Hathaway (a psychologist) and McKinley (a physician) is the outcome of decades of research into personality disorders. The revised version, the MMPI-2 was published in 1989 but was received cautiously. MMPI-2 changed the scoring method and some of the normative data. It was, therefore, hard to compare it to its much hallowed (and oft validated) predecessor.
The MMPI-2 is made of 567 binary (true or false) items (questions). Each item requires the subject to respond: "This is true (or false) as applied to me". There are no "correct" answers. The test booklet allows the diagnostician to provide a rough assessment of the patient (the "basic scales") based on the first 370 queries (though it is recommended to administer all of 567 of them). Based on numerous studies, the items are arranged in scales. The responses are compared to answers provided by "control subjects". The scales allow the diagnostician to identify traits and mental health problems based on these comparisons. In other words, there are no answers that are "typical to paranoid or narcissistic or antisocial patients". There are only responses that deviate from an overall statistical pattern and conform to the reaction patterns of other patients with similar scores. The nature of the deviation determines the patient's traits and tendencies - but not his or her diagnosis!
The interpreted outcomes of the MMPI-2 are phrased thus: "The test results place subject X in this group of patients who, statistically-speaking, reacted similarly. The test results also set subject X apart from these groups of people who, statistically-speaking, responded differently". The test results would never say: "Subject X suffers from (this or that) mental health problem".
There are three validity scales and ten clinical ones in the original MMPI-2, but other scholars derived hundreds of additional scales. For instance: to help in diagnosing personality disorders, most diagnosticians use either the MMPI-I with the Morey-Waugh-Blashfield scales in conjunction with the Wiggins content scales - or (more rarely) the MMPI-2 updated to include the Colligan-Morey-Offord scales.
The validity scales indicate whether the patient responded truthfully and accurately or was trying to manipulate the test. They pick up patterns. Some patients want to appear normal (or abnormal) and consistently choose what they believe are the "correct" answers. This kind of behavior triggers the validity scales. These are so sensitive that they can indicate whether the subject lost his or her place on the answer sheet and was responding randomly! The validity scales also alert the diagnostician to problems in reading comprehension and other inconsistencies in response patterns.
The clinical scales are dimensional (though not multiphasic as the test's misleading name implies). They measure hypochondriasis, depression, hysteria, psychopathic deviation, masculinity-femininity, paranoia, psychasthenia, schizophrenia, hypomania, and social introversion. There are also scales for alcoholism, post-traumatic stress disorder, and personality disorders.
The interpretation of the MMPI-2 is now fully computerized. The computer is fed with the patients' age, sex, educational level, and marital status and does the rest. Still, many scholars have criticized the scoring of the MMPI-2.
(From the book "Malignant Self-love: Narcissism Revisited" by Sam Vaknin - Click on this link to purchase the print book, or 16 e-books, or 3 DVDs with 16 hours of video lectures on narcissists, psychopaths, and abuse in relationships: http://www.narcissistic-abuse.com/thebook.html)